多孔铝的低压成形工艺及其影响因素

以纯铝粉和氯化钠为原料,经混合、低压成形、烧结、溶出造孔剂的方法制备多孔铝,分析了影响多孔铝的孔隙率、孔隙结构、渗透性能、冲击变形量的各种因素。结果表明:含氯化钠45%的混合粉体于120 MPa下成形,在655℃烧结3 h后于水浴中将氯化钠溶出,制备出孔隙率为53.4%及渗透流量为0.128 mL.s-1的多孔铝。成形压力对多孔铝的性能影响最为显著,成形压力增大使开孔孔隙率、渗透流量降低,冲击变形量降低,使闭孔孔隙率增大。     

超细SC/Fe2O3@AP核壳结构复合粒子的制备及表征

为了提高AP基复合固体推进剂的燃速,采用反相乳状液法制备了超细柠檬酸钠(SC)/氧化铁(Fe2O3)@高氯酸铵(AP)核壳结构复合粒子,同时对比研究了SC/Fe2O3@AP与SC/Fe2O3-AP普通混合物的热分解特性,并将其应用于AP基复合固体推进剂中,探究2种复合粒子对AP基复合固体推进剂燃烧性能的影响。研究结果表明:与SC/Fe2O3-AP相比,SC/Fe2O3@AP的热分解峰温降低,表观活化能降低了约8.6%,热分解反应活性得到提高,并且含SC/Fe2O3@AP的AP基复合固体推进剂较含SC/Fe2O3-AP的AP基复合固体推进剂的热分解峰温提前。此外,含SC/Fe2O3-AP的AP基复合固体推进剂的燃速为45.33mm/s,含SC/Fe2O3@AP的AP基复合固体推进剂的燃速为46.46mm/s,燃速提高了2.5%。     

超细晶粒硬质合金刀具在加工耐热合金钢中的应用

超细晶粒硬质合金是一种高硬度、高强度和高耐磨性兼备的硬质合金,它的WC粒度一般为0．2～1．0μm以下,大部分在0．5μm以下,是普通硬质合金WC粒度的几分之一到几十分之一,具有硬质合金的高硬度和高速钢的强度。其硬度一般为90～93HRA,抗弯强度为2000～3500MPa,比含钴量相同的一般WC-Co硬质合金要高,     

铝铸铁

各种不同性能的 Fe-C-Al 合金具有各不相同的组织。之所以会形成这些不同的组织是由于不同合金的石墨化倾向不同和组织中特殊相的形成。当铸铁中的含铝量为5%～8%时,其组织为含铝的铁素体 Fe_3AlCx(v'相)和一定数量的石墨,在含铝11%～17%的铸铁中,     

铝铸铁的铸造

铝铸鉄是铝和普通铸鉄组成的合金。工业中常用的有两种:(1)含铝量大于18％的高铝铸鉄,机械性能为:σ_b=11～17公斤/毫米~2,α_k=0.1公斤·米/厘米~2,H_B=170～240公斤/毫米~2;(2)含铝量小于8％的低铝铸鉄。后者由于工作温度不高(低于700～800℃),所以应用不广。至于含铝在8～18％范围内的,因为硬脆,不能机械加工,所以没有得到实际应用。总的说来,铝能在该铸铁表面形成一层氧化膜,故     

HTPB/镁铝合金含量对含硼富燃推进剂压强指数影响

通过推进剂的燃速、热重(TG-DTG)分析和高压差示扫描(DSC)分析手段研究了端羟基聚丁二烯(HTPB)/镁铝合金(MA)含量变化对含硼推进剂压强指数的影响。采用燃速u与压强P的关系u=apn,求出该推进剂的压强指数n(压强范围0.5 MPa~1.5 MPa)。燃速测试实验结果表明,当HTPB/MA含量为27.3%/3%时,压强指数为0.280,而当HTPB/MA含量为20.3%/10%时,压强指数升高到0.420。通过推进剂的TG-DTG和DSC热分析可知,含硼推进剂中HTPB含量较低、MA含量较高时,推进剂失重较快,且推进剂的热分解受到压强的影响显著增强,特别是氧化剂高氯酸铵(AP)的低温分解受压强影响非常显著,因而燃速较高,压强指数也高。     

新型数控机床用镁铝合金的组织与性能研究

在AZ91镁铝合金中添加少量的合金元素Sc、Er和Ti,制备了数控机床用新型镁铝合金,并进行了显微组织、物相组成、不同温度下的耐磨损性能和力学性能的测试与分析。结果表明,该新型镁铝铸态合金由α-Mg基体以及少量的Mg17Al12、Mg2Sc、(Mg,Zn)4Er组成。与商用AZ91合金相比,该新型镁铝合金在20℃时的磨损体积减小73%、抗拉强度从250MPa增加至294MPa、延伸率从7%增加至12%,在400℃时的磨损体积减小69%、抗拉强度从73MPa增加至253MPa、延伸率从26%增加至42%。     

铸造铝－硅－颗粒氧化物复合材料的磨损研究

研究了铸造Ａｌ－Ｓｉ颗粒氧化物复合材料中Ｃｒ２Ｏ３、Ａｌ２Ｏ３含量和粒度对材料磨损性能的影响；探讨了石墨对该复合材料磨损性能的影响。结果表明，含３％～４％（ｗｔ）颗粒氧化物的铝基复合材料呈现出较好磨损性能；而且在本试验条件下，含粒度较粗氧化物的铝基复合材料的磨损性能较好。作者认为，在较大载荷下，颗粒氧化物对配偶件（４５钢）的磨损影响不大。     

焊接铝蜂窝板焊接技术的研究

文章介绍了焊接铝蜂窝板的结构特征及其工艺特点,并进行焊接铝蜂窝板熔化焊的工艺试验。结果表明：随炉样块中的焊接铝蜂窝板面板的平均拉强度达到了182MPa,比焊接铝蜂窝板面板原材料的平均抗拉强度高出了50MPa。经熔化焊后的焊接铝蜂窝板面板焊接接头的平均抗拉强度为136MPa,达到了焊接铝蜂窝板面板强度的74%以上。经熔化焊后的铝蜂窝板的平压强度和平拉强度均有不同程度的减小,弯曲强度基本没有变化。     

含ACP的无烟改性双基推进剂燃烧特性研究

快燃物ACP作为一种有效含能助剂用来提高推进剂的燃速具有一定的效果。通过DSC和TG-DTG研究了ACP对无烟改性双基推进剂(CMDB)热分解特性的影响,采用靶线法研究了不同含量的ACP对无烟改性双基推进剂燃速和燃速压力指数的影响,用燃烧火焰单幅照相技术和微热电偶测温获得了含ACP无烟改性双基推进剂在稳态燃烧条件下的火焰结构和燃烧波温度分布,分析了该推进剂中主要组分对燃烧性能的影响。结果表明:含ACP推进剂的燃速随ACP含量的增加而增大,推进剂燃烧火焰结构随ACP含量增加而更加明亮。     

纳米氧化物燃烧催化剂在固体推进剂中的应用

纳米氧化物包括单一纳米过渡金属氧化物（纳米Fe2O3和Fe3O4,纳米CuO和Cu2O,纳米PbO、Bi2O3、NiO）、单一纳米稀土氧化物和纳米复合金属氧化物。文中旨在研究纳米氧化物燃烧催化剂在固体推进剂中的应用.     

Experimental and numerical modelling of the ignition of solid propellant

Mixing processes of solid propellants can result in friction. Solid propellant ignitions can be observed under safety tests. Analysing a solid propellant elementary friction test from a mechanical, thermal, and physiochemical point of view, it appears that specific friction conditions allow the emergence of component flows in the solid propellant volume, readying the self-ignition. Numerical simulations of the solid propellant elementary friction test involve discrete elements to model these dynamic behaviours of the components within the contact.Indeed, comparisons between experiments and simulations are performed on mechanical parameters and on the evolution of the solid propellant components within the contact. Such comparisons exhibit qualitative and quantitative results by validating local parameters (adhesion), which make understand the solid propellant ignition scenario.     

X-ray visualization measurement of slurry flow in solid propellant casting

Simulated solid propellant slurry containing lead sphere tracers is experimentally cast into a double-circular cylindrical container. During the casting, the temperature and the pressure environment has been mimicked to an actual composite solid propellant casting of solid rocket motors. X-rays are projected on to the slurry flow from two directions and penetration images are recorded by a flat-panel detector and an X-ray image intensifier. By suppressing the mutual interference of the X-rays, the two-directional X-ray photography has been successfully conducted. Using the time series data of the X-ray images from the two directions, the identification of each tracer particle in space and time has been done and their three-dimensional paths have been computed. From these procedures, the flow field or the velocity field inside the slurry flow, which is usually invisible, has been estimated.     

Numerical simulation of the unsteady combustion of solid rocket propellants at a harmonic pressure change

This study focuses on a numerical investigation of the unsteady burning rate of solid propellants at a harmonic pressure change in the combustion chamber of a solid propellant rocket engine. The physico-mathematical model includes the equations of heat transfer and decomposition of the oxidizer in the solid phase and two phases, the dual velocity, and the two-temperature reaction flow of gasification products. The boundary conditions on the solid fuel surface implement the conservation of energy fluxes and the mass of components. We numerically calculate the unsteady burning rate of metallized solid propellant and nitroglycerin powder under a harmonic pressure change in the combustion chamber of a solid propellant rocket engine and determine the dependence of the burning rate amplitude on the frequency of pressure oscillations. The amplitude of the burning rate depends nonmonotonously on the oscillation frequency. With increasing frequency, the amplitude first rises and then declines.

     

Residual stress measurement on propellant tank of 2219 aluminum alloy and study on its weak spot

This paper presented residual stress measurement on two circumferential Variable polarity plasma arc welding (VPPAW) joints and one circular closed Friction stir welding (FSW) joint on the propellant tank of 2219 aluminum alloy using the indentation strain-gauge method. Quite large tensile residual stresses were attached to the center and inner areas of the circular closed FSW joint. There were very large tensile stresses in some points of the two circumferential VPPAW joints, among these points, the maximum value was +253 MPa, which was about 63 % of the yield strength of 410 MPa measured in the base material. In addition, the peak of compressive residual stress was about -160 MPa. Above all, there were two typical peaks of residual stress in the circumferential VPPAW joints, one was located in the middle part while the other one was near the start/end position of the joints. Combining the result of residual stress measurement with the characteristics of the tank structure, it can be concluded that circular closed FSW joint around the flange was a weak spot on the propellant tank. And the most vulnerable point on the circular closed FSW joint has also been found.     

固体火箭发动机推力向量控制系统动态性能分析

以某型号固体火箭发动机推力向量控制系统为研究对象,采用多体系统动力学计算方法,以作用在系统活动体上的轴向载荷为工作阻力,作动器指令位移为原动件的已知运动规律,接头内引入并联非线性弹簧阻尼器表征各构件间的接触,建立该型号推力向量控制系统动力学模型,进行多体动力学计算,得到接头内构件间的实时运动规律、接触力及力矩。理论计算与系统冷摆试验相结合,分析作动力矩与摆角、频率的关系,计算接触变形产生的力矩增量,分析接头压痕产生的主要原因,并提出改进措施。     

压缩式封隔器洗井活塞密封性能仿真研究

压缩式封隔器通过液压油驱动洗井活塞运动从而完成油层或水层间的隔离,活塞的有效密封是保证封隔器正常工作的前提。通过建立O形密封圈的非线性有限元分析模型,对配合外径为115.7 mm,厚度分别为5.3 mm和3.55 mm的两种O形圈进行了分析,通过密封圈接触面最大接触压力判据,得到两种结构密封圈的临界工作压力为8.4 MPa和7.6 MPa。依据Von Mises应力对密封圈进行仿真校核的结果表明所分析结果是正确的。所得研究成果可对O形密封圈的设计与使用提供理论依据,为提高封隔器的可靠性从而确保油气勘探开发的安全进行提供指导。     

基于PMAC和组态的推进剂模拟整形系统

介绍了基于PMAC和组态的远程监控系统在小型固体火箭推进剂模拟整形系统中的应用,数控系统以PMAC及PLC为核心,通过模拟加工、数据采集实现了系统的远程监控。数控系统的控制方式灵活方便,得到的实验数据为固体火箭推进剂模拟整形的进一步研究提供了宝贵的依据。     

Investigation on MoS2 and graphite coatings and their effects on the tribological properties of the radial spherical plain bearings

With constant enlargement of the application areas of the spherical plain bearings, higher quality lubrication of the bearings is required. To solve the lubricating problems of spherical plain bearings under high temperature, high vacuum, high speed, heavy loads and strong oxidation conditions, it is urgent for us to develop more excellent self-lubricating technologies. In this paper, the bonded solid lubricant coatings, which use inorganic phosphate as the binder, the mixture of MoS2 and graphite with two different weight proportions as the solid lubricant, are prepared by spraying under three different spray gun pressures. The bonding strength tests on the coatings show that the best spraying pressure is 0.2 MPa and the better mixing proportion of MoS2 to Graphite is 3:1. Then for the radial spherical plain bearings with steel/steel friction pair, after the coatings are made on the inner ring outer surfaces, the friction coefficient, the wear loss and the friction temperature of the bearings under four oscillating frequencies are investigated by a self-made tribo-tester. The test results, SEM of the worn morphologies and EDS of worn areas show that tribological properties of the bearing are obviously improved by the bonded solid lubricant coatings. When sprayed under the spray gun pressure of 0.2 MPa, the bearings have better anti-friction and anti-wear properties than those sprayed under 0.1 MPa and 0.3 MPa. Further as proved from the XPS analysis, between the coating with 3:1 mixing ratio of MoS2 to Graphite and the coating with 1:1 ratio, the former has less oxidation occurred on the surface and therefore has better tribological characteristics than the latter. This paper provides a reference to developing a new product of the radial spherical plain bearings with high bonding strength, oxidation resistance and abrasion resistance.